import java.util.HashMap;


public class SymExpr extends Expr {
	String varname;
	public SymExpr(HashMap syms, String varname) {
		this.varname = varname;
		this.syms = syms;
	}
	public Integer run() {
		Expr e = syms.get(varname);
		if(e == null)
			return -1;
		else
			return e.run();
	}
}
